1. Field of the Invention
The present invention relates to an absorption pad for an immunoassay, a strip for an immunoassay and an immunoassay apparatus, and particularly relates to an absorption pad for the immunoassay, which is remarkably excellent in water absorptivity, and a strip for the immunoassay and an immunoassay apparatus, which use the absorption pad and shorten a detection time, as well as uses thereof.
2. Description of the Related Art
Analyses of biological components or drugs included in specimens such as blood and urine are important for diagnosis of a pathological condition and determination of a therapeutic process. Thus, an immunoassay apparatus which measures using an antigen-antibody reaction has been used as the apparatus for simply detecting the biological component and the drug.
Conventionally, biological samples collected from the blood, urine and mucosal secretion have been analyzed immunologically in the diagnosis of the pathological condition and the determination of the therapeutic process. An enzyme immunoassay apparatus using the antigen-antibody reaction has been developed as the apparatus used for immunological analyses (see Japan Patent No. 3,248,436; Japan Patent No. 3,284,896; JP 2005-503556-A; JP 2005-83927-A).
In the enzyme immunoassay apparatus, for example, a sandwich complex is formed by antigen-antibody reactions among three, i.e., an antigen or antibody in a specimen, an enzyme-labeled form of an antibody or antigen which reacts with said antigen or antibody, and an antibody or antigen which reacts with said antigen or antibody, and the presence or absence of the complex is detected using a substrate which develops a color by reacting with the enzyme. In these apparatuses, an end corresponding to a downstream of the apparatus is provided with an absorption pad because each component is sequentially dissolved in a developing buffer and the solution is moved in a constant direction in the apparatus (see JP 2005-503556-A).
The absorption pad is made up of an absorptive material, and for example, it has been described that nonwovens made from absorptive filter papers or glass fibers, porous materials and fibrous members are applicable (JP 2005-83927-A).
However, the water absorptivity is insufficient in any absorption pads using the conventional absorptive materials, and it takes some time to detect a result in the apparatus using such a material. Particularly, when the antigen or antibody derived from an infectious disease is subjected to the measurement, it is better that the detection time is as short as possible in terms of rapid treatment and preventing the spread of the infectious disease.
Meanwhile, the conventional immunoassay apparatus is manufactured by individually laminating each member in a cassette, and thus, the water absorptivity can be enhanced by utilizing one having a relatively wide width as the absorption pad. However, in recent years, a laminate system in which all members including the absorption pad are adhered with seals to integrate and then housed in the cassette has been becoming a mainstream. In this case, one having the narrow width is often used as the absorption pad for enhancing production efficiency. Thus, the absorption pad in line with the recent production system, which is remarkably excellent in water absorptivity, has been required.
Here, an ordinarily possible principle as a procedure to shorten the detection time in the immunoassay apparatus may include the enhancement of capillarity by expanding pores in a membrane part where the developing buffer is absorbed and moved. However, when the pores are expanded, a determination line which shows a determination result is not expressed sharply.